Seismic overstrength and ductility of concrete buildings reinforced with superelastic shape memory alloy rebar

Abstract

The use of superelastic shape memory alloys (SMAs) as a reinforcing material in concrete structures is gradually gaining interest among researchers. Because of SMAs’ different mechanical properties compared to regular steel, use of SMA as reinforcement in concrete may change responses of structures under seismic loads. In this study, the effect of SMA as reinforcement in concrete structures is analytically investigated for three different storeys (3, 6 and 8) reinforced concrete (RC) buildings. For each building, three different reinforcement detailing are considered: (i) steel reinforcement (Steel) only, (ii) SMA rebar used in the plastic hinge region of the beams and steel rebar in other regions (Steel-SMA), and (iii), beams fully reinforced with SMA rebar (SMA) and steel rebar in other regions. For each case, columns were reinforced with steel rebar. Nonlinear static pushover analyses were performed to determine the overstrength and ductility of Steel, Steel-SMA and SMA RC buildings. Furthermore, nonlinear dynamic time history analyses were also performed using an ensemble of ten earthquake records to determine the seismic demand and capacity ratio in terms of base shear and drift for each type of RC building. Results obtained from the analyses confirm the seismic performance of low and medium rise frames while utilizing SMA as reinforcement.